Allyl alcohol is the simplest unsaturated alcohol represented by CH2═CHCH2OH, and is employed as a pesticide or is importantly utilized as a feed material or an intermediate in the course of producing many compounds. Furthermore, it may be used as an antiseptic, or applied in a variety of fields, including preparation of phthalic acid ester useful as a polymer plasticizer, preparation of butane-1,4-diol as a monomer of polyester (PBT), or production of acrylic acid.
Thorough research is ongoing into preparation of allyl alcohol, including reacting propylene, acetic acid and oxygen to give allyl acetate that is then hydrolyzed into allyl alcohol based on petrochemical processes. Also, as for eco-friendly preparation processes of allyl alcohol using bio materials compared to conventional petrochemical processes, when glycerol is reacted with formic acid, allyl alcohol may be obtained at high yield even in the absence of a catalyst, which is disclosed in U.S. Pat. No. 8,273,926. Useful as the material for allyl alcohol in such a registered patent, glycerol is a byproduct mainly resulting from preparation of biodiesel, and is currently utilized as a material for medical or cosmetic products, a solvent or lubricant. Since the supply of a glycerol byproduct is expected to increase in proportion to an increase in production of biodiesel, new applications, in addition to conventional glycerol uses, are under study. However, in order to maximize the yield of allyl alcohol in the above patent, formic acid has to be excessively added (e.g. 1.45 equivalents) relative to glycerol. In this case, the present inventors expect that the drawbacks such as long reaction time and complicated processing steps may occur, despite high allyl alcohol yield. As illustrated in FIG. 1, due to excessive use of formic acid and low product selectivity of allyl alcohol, gas phase products obtained via (a) according to a conventional technique include CO2, H2O (W, by 100° C.), allyl formate (AF, by 80˜83° C.), and allyl alcohol (AA, by 97° C.), with a large amount of unreacted formic acid (FA, by 100.8° C.). Also, allyl alcohol in the liquid reaction products obtained from (b) through a gas separator has a low concentration, undesirably increasing energy and cost required for the separation process thereof. Since the difference of boiling points of W, AA and FA as the gas phase products is very small, it is impossible to separate such products via typical distillation. Furthermore, due to the azeotropes of formic acid-water (FA-W) and allyl alcohol-formic acid-water (AA-FA-W), it is very difficult to separate formic acid from these products. Hence, in order to prepare allyl alcohol on a commercial scale, the liquid reaction products should contain allyl alcohol in a large amount and also the production of allyl formate byproduct and the production of unreacted formic acid should be minimized, and thereby it is possible to easily perform the subsequent separation process. Accordingly, there is a need for a novel synthesis method able to drastically increase the concentration of allyl alcohol from glycerol under specific synthesis conditions.